JPS59120763A - Variable venturi carburetor - Google Patents

Abstract

PURPOSE:To control an air-fuel ratio properly at all times by providing mutliple nozzles in series on a variable nozzle body with a fixed needle inserted into a suction piston and opening an auxiliary fuel passage with its passage area controlled in response to the engine operation condition between nozzles. CONSTITUTION:When the suction negative pressure generated in response to the opening of a throttle valve 33 is introduced into the negative pressure chamber 21 of a variable venturi section in the said carburetor, a suction piston 35 is moved upward against a spring 22 and a jet needle 55 is extracted from a variable nozzle body 38, thereby the nozzle opening area is varied. At this time, two nozzles 39, 40 are formed apart in series on the upper end section of the movable nozzle body 38, and an auxiliary fuel passage 43 is formed on a fixed section 34 so as to be opened between both nozzles 39, 40. A control valve 44 is provided in the auxiliary fuel passage 43, and the valve 44 opens or closes a valve body 45 through a diaphragm 54 in response to the suction negative pressure introduced into a negative pressure chamber 39 through a negative pressure passage 52.

Description

DETAILED DESCRIPTION OF THE INVENTION [1] Technical Field The present invention relates to a variable venturi carburetor, and more particularly to a variable venturi carburetor that can always obtain an appropriate air-fuel ratio depending on the operating conditions of an engine.

[2] Prior art In general, in variable venturi carburetors, the venturi area automatically changes according to the amount of intake air, and the negative pressure in the venturi part is kept constant and the amount of fuel corresponding to the change in the venturi area is pumped out to the bench. This is to keep the air-fuel ratio of the mixture constant.

As such a conventional variable venturi carburetor, for example, the one shown in Figure 1.2 is known (see Takashi Yoshida's "Theory and Practice of Carburetor" published by J Railway Japan Co., Ltd.). The carburetor can be roughly divided into two parts: a venturi system part 1 that supplies fuel to the venturi part in an amount corresponding to changes in the venturi area and keeps the air-fuel ratio of the mixture constant, and a float system that supplies fuel to this venturi system part 1. Part 2
It consists of and. The venturi system part 1 is disposed upstream of a throttle valve 4 provided in an intake passage 3 communicating with the engine, and a venturi part 6 is formed between the venturi fixing part 5 and the fixing part 5. It has a hennary movable part 7. The venturi fixing part 5 is a fixing part 8 formed in a flat shape on the lower wall of the intake passage 3 and protruding into the intake passage 3.
A substantially cylindrical nozzle guide 9 is provided at the center of the fixed portion 8. The upper end of the nozzle guide 9 opens into the fixing part 8, and an idle adjusting nut 10 is screwed into the lower end. A spring 12 is compressed between the idle adjuster 10 and an intake pipe 11 forming the intake passage 3. A nozzle body 13 that supplies fuel to the intake passage 3 is slidably housed in the nozzle guide 9. The upper end of the nozzle body 13 opens toward the fixed part 8, and this opening constitutes a nozzle 14. are doing. A connector 16 to which a lever 15 is attached is screwed into the lower end of the nozzle body 13.
6 is constantly urged upward in the figure by a spring (not shown). The lever 15 is used to automatically or manually push the nozzle body 13 downward in the figure when starting the engine, thereby increasing the amount of fuel injected into the fixed part 8. Fuel is supplied into the nozzle body 13 through a connector 16 and a fuel vibrator 17 from a flow I system section 2, the details of which will be described later.

On the other hand, the hennary movable part 7 is disposed on the upper wall side of the intake passage 3 facing the fixed part 8, and includes a suction cylinder 18, a suction piston 19 housed in the suction cylinder 18 so as to be able to move vertically, have. The suction piston 19 forms a venturi part 6 between its lower end surface and the fixed part 8, and an atmospheric pressure chamber 20 to which atmospheric pressure is guided inside the suction cylinder 18 and a negative pressure chamber to which the negative pressure of the venturi part 6 is guided. It is defined as 21. A suction spring 22 is compressed in the negative pressure chamber 21, and the suction spring 22 is connected to the suction piston 1.
9 is always urged downward (in the direction of the fixed part 8). The suction piston 19 moves toward and away from the fixed part 8 by the negative pressure of the venturi part 6 guided to the negative pressure chamber 21, thereby making the hennium area variable. Further, a tapered jet needle 23 is fixed to the lower end of the Zakujo piston 19, and the jet needle 23 is connected to the nozzle 14.
It penetrates through and is loosely inserted into the nozzle body 13. This jet needle 23 forms an annular metering section between it and the nozzle 14, and moves up and down within the nozzle body 13 in accordance with the vertical movement of the suction piston 19. is increased as the suction piston 19 moves away from the fixed part 8.

Note that 24 is an oil damper, and the oil damper 24 not only suppresses the sudden rise of the suction piston 19 but also prevents vibration of the suction piston 19 due to pulsation of intake air.

Next, the float system section 2 that supplies fuel to the venturi system section 1 has a float chamber 25 that communicates with the fuel vibrator 17.
, a float 26 housed in the float chamber 25, and a needle valve 2 that is opened and closed by the floating of the float 26.
7.

The float chamber 25 has two to two fuel tanks (not shown).
Fuel is supplied through the dollar valve 27 and the float chamber 2
The float 26 floats to open and close the needle valve 27 according to the amount of fuel supplied to the valve 5.

Therefore, the amount of fuel in the float chamber 25 is kept constant, and a predetermined level of fuel is always supplied into the nozzle body 13 from the float chamber 25.

In such a variable henna vaporizer, the negative pressure generated in the henna portion 6 due to the intake air to the engine is transferred to the negative pressure chamber 21.
Since atmospheric pressure is introduced into the atmospheric pressure chamber 20, when the pressure difference between the negative pressure chamber 21 and the atmospheric pressure chamber 20 is greater than a predetermined value, the suction piston 19 moves upward. It moves and stops at a position where the biasing force of the suction spring 22, the weight of the suction piston 19, and the negative pressure generated in the venturi portion 6 are balanced. That is, the suction piston 19 moves up and down according to the amount of intake air, changes the venturi area of the venturi section 6, and keeps the air flow velocity and negative pressure of the venturi section 6 constant. At this time, fuel is ejected from the nozzle 14 to the venturi section 6 due to the negative pressure generated in the venturi section 6, mixed with intake air, and supplied to the engine. Also, depending on the vertical movement of the suction piston 19, the nozzle 14 and the nozzle 23
The area of the passage between the two, that is, the area of the passage of the measuring part changes, and the amount of fuel injected to the venturi part 6 changes. Therefore, fuel corresponding to the amount of intake air is ejected from the venturi portion 6c, and a mixture having a predetermined air-fuel ratio is supplied to the engine.

However, in such a conventional variable venturi carburetor, the amount of lift of the suction piston 19 is determined by the amount of intake air of the engine, and the amount of lift of the suction piston 19 is determined by the amount of air taken into the nozzle 14 and the jet needle. 23, the air-fuel ratio was determined uniquely by the amount of intake air. Therefore, there is a problem in that it is not possible to supply an appropriate amount of fuel corresponding to various operating conditions that require different air-fuel ratios even with the same amount of intake air. That is, at low speeds and high loads, an air-fuel ratio of 11 to 13 is required for the output-oriented air-fuel mixture and U7, while at medium-high speeds and low loads for the same amount of intake air, an air-fuel ratio leaner than the former is required as an economy-oriented air-fuel mixture. However, in the conventional variable Hentschuri carburetor, the air-fuel ratio becomes the same in both of these operating conditions, and it is not possible to supply an appropriate amount of fuel corresponding to the operating condition, making it difficult to satisfy the required air-fuel ratio. I can't.

[3] Purpose of the Invention Therefore, the present invention arranges a plurality of nozzles in series in a movable nozzle body, provides an auxiliary fuel passage that communicates between each nozzle and a fixed part, and reduces the passage area of this auxiliary fuel passage. The purpose is to satisfy the required air-fuel ratio by supplying an appropriate amount of fuel corresponding to the engine operating state to the fixed part by performing control based on the engine operating state.

[4] Structure of the Invention The variable venturi carburetor according to the present invention includes a fixed part provided upstream of the throttle valve in the intake passage, a nozzle body movably disposed in the fixed part, and a nozzle body formed in the nozzle body. ,
A venturi part is formed between the nozzle that supplies fuel to the intake passage, the fuel passage that supplies fuel to the nozzle, and the fixed part, and the negative pressure of the venturi part moves toward and away from the fixed part, causing the venturi to move toward and away from the fixed part. It is equipped with a suction piston whose area is variable, and a jet needle whose tip is loosely inserted into a nozzle and whose nozzle opening area is changed according to movement of the suction piston. A plurality of the nozzles are arranged in series. These nozzles are communicated with the fixed part through an auxiliary fuel passage, and by controlling the passage area of this auxiliary fuel passage based on the operating condition of the engine, an appropriate amount corresponding to various operating conditions of the engine can be obtained. It is configured to supply fuel.

[5] Examples The present invention will be explained below based on the drawings.

3 to 7 are diagrams showing a first embodiment of the present invention. The variable Hentschuri vaporizer shown in this figure is one in which a Hentschuri system part and a flow l-system part are integrally assembled. In FIG. 3, 31 is an intake passage formed in an intake pipe (carburizer main body) 32 that communicates with the engine, and is a lower wall on the upstream side of a throttle valve 33 that is interlocked with an accelerator pedal provided in the intake passage 31. A flat fixing portion 34 protruding from the intake passage 31 is formed in the intake passage 31 .

A suction piston 35 housed in a suction cylinder (not shown) is disposed on the upper side of the intake passage 31 facing the fixed part 34.
The lower end surface of 5 and the fixed part 34 have a venturi part 36 between them.
is formed. The suction piston 35 approaches the fixed part 34 due to the negative pressure generated in the venturi part 36.
The Venturi area is made variable by moving the venturi apart. Fixed part 3
4 is formed with a hole 37, and a nozzle body 38 is slidably housed in the hole 37. Nozzle body 3
8, a first nozzle 39 that opens toward the fixed part 34 and a second nozzle 4 located below the first nozzle 39.
0 are formed in series, respectively, and the nozzle body 3
8 has a function as a fuel passage that supplies fuel to each of these nozzles 39 and 40. A lower end portion of the nozzle body 38 is disposed below the fixed portion 34 and projects into a float chamber 41 that supplies fuel to the nozzle body 38 . Fuel is supplied to the float chamber 41 from a fuel tank (not shown), and a float 42 floats according to the amount of fuel in the float chamber 41 to control the amount of fuel supplied into the float chamber 41. . Therefore, the amount of fuel in the float chamber 41 is kept constant, and the nozzle body 38 is always supplied with fuel up to a predetermined level from the float chamber 41. Further, an auxiliary fuel passage 43 is formed in the fixed part 34, and one end of the auxiliary fuel passage 43 is open downstream of the hole 37 formed in the fixed part 34, and the other end is connected to the first nozzle 39 and the second nozzle. The nozzle body 38 is opened between the nozzle body 40 and the nozzle body 38 . Further, a control valve 44 for opening and closing the passage 43 is disposed in the auxiliary fuel passage 43, and the control valve 44 has a valve body 45 whose one end protrudes into the auxiliary fuel passage 43 in response to intake pipe negative pressure. The auxiliary fuel passage 43 is opened and closed by moving it. The control valve 44 includes a casing 47 disposed in a hole 46 bored in the wall of the intake pipe 32, and a casing 47 which is slidably housed in the casing 47 and has an atmospheric pressure chamber 48 and a negative pressure chamber 48 inside the casing 47. It has a piston 50 that defines a pressure chamber 49 and a valve body 45 that is fixed to the upper end of the piston 50 and opens and closes the auxiliary fuel passage 43.

Atmospheric pressure is introduced into the atmospheric pressure chamber 48 through a small hole 51 communicating with the float chamber 41 , and into the negative pressure chamber 49 through a negative pressure passage 52 formed in the wall of the intake pipe 32 downstream of the throttle valve 33 . While the intake pipe negative pressure is introduced, the piston 50
A spring 53 is provided that always urges the air pressure chamber 48 toward the atmospheric pressure chamber 48 (downward in the figure). Further, a diaphragm 54 is provided on the upper wall of the negative pressure chamber 49.
4 is a negative pressure chamber 4 from the auxiliary fuel passage 43 due to the movement of the valve body 45.
This prevents fuel from leaking to 9. Therefore, when the intake pipe negative pressure is equal to or higher than a predetermined value, the control valve 44 moves the piston 50 together with the valve body 45 toward the negative pressure chamber 49 side against the biasing force of the spring 53 due to this negative pressure, and the auxiliary fuel passage 43 is closed, and on the other hand, if the intake pipe negative pressure is less than a predetermined value, the piston 50 moves together with the valve body 45 toward the atmospheric pressure chamber 48 due to the biasing force of the spring 53, and the auxiliary fuel passage 43 is opened (i.e., the The auxiliary fuel passage 43, which communicates between the first nozzle 39 and the second nozzle 40 and the fixed part 34, is opened and closed based on the operating state of the engine (in this embodiment, the intake pipe negative pressure).

On the other hand, a tapered jet needle 55 fixed to the lower end of the suction piston 35 is loosely inserted into the first nozzle 39 and the second nozzle 40.
An annular first measuring part 56 and a second measuring part 57 are respectively formed between each part of the nozzle 9 and the second nozzle 40 and the needle 55. The diameter of the second nozzle 40 located on the upstream side of the nozzle body 38, which is a fuel passage, is formed larger than the diameter of the first nozzle 391, and the passage area of the second liquor metering section 57 is equal to that of the first metering section 5G. larger than the aisle area. As the Zakujo piston 35 moves,
The jet needle 55 moves up and down to change the passage area of the first measuring section 56 and the second measuring section 57. This change is an inferior change in that since the jet needle 55 is formed in a tapered shape, the area of each passage increases when the jet needle 55 moves upward in the figure. Furthermore, 58
is an idle adjustment bolt 58 that adjusts the set position of the nozzle body 38 within the hole 37 to change the air-fuel ratio when the engine is idling.

Next, the effect will be explained. Even if the engine has the same amount of intake air, the required air-fuel ratio differs depending on the operating state. For example, in operating states A and B located on the equal intake air amount line in FIG. Operating state B, where the intake pipe negative pressure is small, requires a rich air-fuel ratio (output-oriented air-fuel ratio: around 11.5) as shown by the area in FIG. Incidentally, FIG. 5 shows the relationship between torque and fuel consumption rate with respect to the air-fuel ratio when the engine speed is constant (2000 rpffI>. Therefore, the auxiliary fuel passage 43 is opened and closed by the control valve 44 when a predetermined negative pressure is reached. In this embodiment, the air-fuel ratio required under various operating conditions of the engine is satisfied.When the intake pipe negative pressure exceeds a predetermined negative pressure, the control valve 44 closes the auxiliary fuel passage 43. , the control valve 44 opens the auxiliary fuel passage 43 when the predetermined negative pressure is lower than the predetermined negative pressure.

Here, for the first measuring section 56, its passage area is A, its flow coefficient is 01, its downstream pressure (approximately equal to Hentschuri negative pressure) is P3, and for the second measuring section 57,
Its passage area is A2, its flow rate coefficient is C2, and its upstream pressure (pressure inside the nozzle body 38, that is, the fuel passage) is P.

Then, when the auxiliary fuel passage 43 is closed and when it is open, the respective fuel flow rates QA and QB sucked into the intake passage 31, that is, the fixed part 34, are given by the following equations.

Uh, /〈≧3 Near!・(P knee” P,
)---(21Q[3=C2A2°) where g is the acceleration of gravity, γ is the fuel specific weight, and X is the effective passage area ratio, which is given by the following equation.

As is clear from equations (1) and (3), the fuel flow when the auxiliary fuel passage 43 is closed is the first metering section 56.
and the second measuring section 57. On the other hand, the fuel flow rate QB when the auxiliary fuel passage 43 is open is determined only by the second measuring section 57, as is clear from equation (2). In this case, the fuel flow rate is given by a formula for the fuel flow rate QA, and the relationship in this formula (4), that is, the relationship between the effective passage area ratio X and the flow rate ratio QB/QA is as shown in FIG. In addition, the air-fuel ratio (A/F
) and the effective passage area ratio X have a relationship as shown in FIG. For example, if the effective passage area ratio X is X = 0
．． 9, the flow rate ratio Q B /, Q A has a value of 1.49 from equation (4). Furthermore, under this condition (X=0
．． 9), the air-fuel ratio (A/F) A at the fuel flow rate QA is set to 1.
8, the air-fuel ratio Y becomes 0.67 as shown in FIG. 7, so the air-fuel ratio at the fuel flow rate Q8 (
A/F) B is 18 x O, 67 = 12.1.

Therefore, by appropriately setting the effective passage area ratio X of the first nozzle 39 to the second nozzle 4o, it is possible to obtain both the economy-oriented air-fuel ratio and the power-oriented air-fuel ratio required by the engine for the same amount of intake air. I can do it. That is, in the case of the above example, since the effective passage area ratio X is 0.9, the air-fuel ratio in operating state A in FIG.
When set to , a driving letter! 3B has an air-fuel ratio of 12.1 (5th
Figure area D) can be obtained.

Further, the variable venturi carburetor according to this embodiment opens and closes the auxiliary fuel passage 43 based on the intake pipe negative pressure, and can change the air-fuel ratio even with the same amount of intake air.In other words, it has a power enrich function. In other words, it has a function of enriching the air-fuel ratio when the engine is under high load. The power enrichment function according to this embodiment can be applied to other devices,
For example, unlike negative pressure power equipment and mechanical power equipment,
When a rich air-fuel ratio is required, the auxiliary fuel passage 43 opens, and in response to changes in the amount of intake air, that is, in accordance with the lift amount of the Zakujoon piston 35, an amount corresponding to the amount of intake air is supplied from the second measuring section 57. of fuel is measured and fixed part 3
4, the power can be enriched over a wide operating range. Therefore, in this embodiment, if the power system is set to operate under a predetermined condition as in the case of other dual-connected devices, the air-fuel ratio may become too rich at low rotation speeds where the amount of intake air is smaller than that condition. Furthermore, it is possible to eliminate the inconvenience that the air-fuel ratio becomes lean on the high rotation side where the amount of intake air is large. Furthermore, the power enrichment function according to this embodiment increases the amount of fuel supplied by opening the auxiliary fuel passage 43 even at the time of starting with a small intake negative pressure, and acts as a starting enricher that satisfies a rich air-fuel ratio at the time of starting. You can also do it.

FIG. 8 is a diagram showing a second embodiment of the present invention. In explaining this embodiment, only the same reference numbers will be used for the same components as those in the first embodiment, and the explanation thereof will be omitted. do. Normally, the air-fuel ratio required by the engine changes as shown in FIG. 9 depending on the warm-up state of the engine. Therefore, this embodiment is provided with a control valve 6e that changes the passage area of the auxiliary fuel passage 43 according to the warm-up state of the engine.

However, the valve body 62 of the control valve 61 is formed into a tapered shape, and is moved in the direction of opening the auxiliary fuel passage 43 by the spring 63.
At the same time, the thermowax 64 receives an urging force due to thermal expansion of the thermowax 64 in a direction to close the auxiliary fuel passage 43, and the mowax 64 is introduced into a cooling water chamber 65 surrounding the thermowax 64. Its volume changes depending on the temperature of the engine cooling water. However, control valve 61
When the cooling water temperature is low, the auxiliary fuel passage 43 is opened wide,
The auxiliary fuel passage 43 is closed as the cooling water temperature increases.

Here, when the cooling water temperature is low and the valve body 62 fully opens the auxiliary fuel passage 43, the fuel flow iQ sucked into the fixed part 34.
B is the flow rate determined by the second measuring section 57 and expressed by the following formula. - Horn, after warming up, valve body 62 or secondary combustion*, 1 passage 4
The fuel flow rate QH when 3 is fully closed and 7 is the first and second a1.
The flow rate is expressed by the following formula (6) for each of the parts 9 and 56.57. These (5), (6)
As is clear from the equation, when the cooling water temperature is low, the fuel flow rate can be increased by one inverse of the fuel flow rate after warming up. Further, during warm-up, the value of the fuel flow rate can be gradually changed from Qc to QH in accordance with the passage area of the auxiliary fuel passage 43, which changes depending on the cooling water temperature.

For example, as shown in Figure 9, after warming up (cooling water temperature 80°C:
If the air-fuel ratio at point E in Figure 9 is 15, the effective passage area ratio X is set to 0.6 and the cooling water temperature is 0°C (
Point F in FIG. 9) The control valve 61 is set in advance to fully open the auxiliary fuel passage 43 at the following times.) As is clear from FIG. 6, the fuel flow rate ratio Oc//Q, 4 is 1
．． 94, and from the relationship shown in Figure 7 (because the air-fuel ratio Y at this time is 0.51), the air-fuel ratio at point F in Figure 9 becomes 15 X O,51' = 7.7. It is possible to supply fuel with a rich air-fuel ratio when the cooling water temperature is below 0°C. Furthermore, during the warm-up period when the coolant temperature is 0°C or higher, the operation of the thermowax 64, which changes its volume according to the coolant temperature, is controlled by the valve body 62 or the auxiliary fuel passage 43 so that the passage area matches the air-fuel ratio required by the engine. (i.e., the setting shown in the shaded area G in Fig. 9), it is possible to increase the pressure loss (intake loss) by, for example, installing a choke valve in the middle of the intake passage. Compared to the method of not changing the required air-fuel ratio, there is no intake loss,
The requirements of the engine can be satisfied extremely efficiently.

FIG. 10 is a diagram showing a third embodiment of the present invention, and the first
Components that are the same as those in the embodiment are designated by the same reference numerals, and their explanations will be omitted. In this embodiment, the air-fuel ratio is feedback-controlled based on the operating state of the engine. 71 is an electromagnetic control valve that controls opening and closing of the auxiliary fuel passage 43; the electromagnetic control valve 71 has a valve body 72 whose one end is inserted into the auxiliary fuel passage 43; It has a spring 73 that biases, and a solenoid coil 74 that draws in a direction in which the valve body 72 opens the auxiliary fuel passage 43 when energized. Solenoid coil 74
A pulse signal having a predetermined frequency and whose duty ratio is controlled is inputted to the input terminal 1, and this duty ratio control is performed by the method shown schematically in FIG. 11. That is, engine 75
An oxygen sensor 77 disposed in the exhaust passage 7G detects the exhaust oxygen concentration and inputs this to the control unit 78 as a signal indicating the operating status of the engine, and the control unit 78 receives this input. The signal value is compared with the signal value when the air-fuel ratio required by the engine is satisfied. Then, the control unit 78 generates a pulse signal whose duty ratio is controlled to open and close the electromagnetic control valve 71 disposed in the carburetor 79 so that the input signal value matches the signal value when the required air-fuel ratio is satisfied. Output. This pulse signal has a predetermined frequency, and its pulse width is a signal whose duty ratio is controlled. For example, when a rich air-fuel ratio is required, the 12th
ON time t during which the electromagnetic control valve 71 is opened as shown in Figure a
When the OFF time when Q is closed is controlled to be long and a lean air-fuel ratio is required, the O
N time to is also OFF time. controlled shorter than

Therefore, as the ON time of the pulse signal becomes longer, the average valve opening time of the electromagnetic control valve 71 becomes longer, and the air-fuel ratio becomes richer. In this manner, the control unit 78 performs feedback control of the electromagnetic control valve 71 to obtain an appropriate air-fuel ratio based on the operating state of the engine. For example, if the effective passage area ratio x is 2 and it is artificial, the solenoid control valve 71 or O
If the air-fuel ratio in the N state is 13.9, then from the relationship shown in Figure 7, the value of the air-fuel ratio Y corresponding to X = 2 is 0.89.
Therefore, it is possible to control the air-fuel ratio by adjusting the width of the solenoid control valve 71 or OI'F (Fi-).

In addition, in this example, JJ + air oxygen hv 4 degrees is displayed, and two units are used to control the air fuel ratio.
Other signals such as combustion focus, cold u, l17 and temperature,
It is possible to control the fee based on the signal indicating the acceleration of the swing, etc. (4-). In addition, in the case of embodiments 1 and 2, the electromagnetic control valve 71 is controlled using the ON (,) t''+; For example, a variable needle and an orifice may be combined to open and control a variable opening.

Appropriately combine each actual JfE example described in +';, -1-.
Then, not only can an air-fuel ratio that can satisfy a wide range of engine operating conditions be easily obtained, but also an inexpensive carburetor with a simple structure and good performance can be obtained.

[6] Effects According to the present invention, an appropriate amount of fuel can be supplied depending on the operating state of the engine, and the air-fuel ratio required by the engine can always be satisfied.

[Brief explanation of the drawing]

Fig. 1.2 is a diagram showing a conventional variable venturi carburetor, Fig. 1 is a front sectional view thereof, Fig. 2 is a side view thereof, and Figs. 3 to 7 are views of a variable venturi carburetor according to the present invention. 1st
FIG. 3 is a sectional view of the main part I, FIG. 4 is a diagram showing the operating state of the engine according to the relationship between engine rotational speed and torque, and FIG. 6 is a diagram showing the relationship between the effective passage area ratio and the flow rate ratio; FIG. 7 is a diagram showing the relationship between the effective passage area ratio and the air-fuel ratio ratio; FIG. 8 is a sectional view of a fixed part showing a second embodiment of the variable venturi carburetor according to the present invention, FIG. 9 is a diagram showing the relationship between engine cooling water temperature and required air-fuel ratio, and FIGS. 10 to 12 is a diagram showing a third embodiment of a variable venturi carburetor according to the present invention,
Fig. 10 is a sectional view of the fixed part, Fig. 11 is a schematic diagram showing the control of the electromagnetic control valve, Fig. 12 shows the pulse signal to the electromagnetic control valve, and Fig. 12a is the valve opening time. Fig. 12 shows the case where the valve opening time is short. 31 - Intake passage, 33 - One throttle valve, 34 Fixed part, 35 - Zakujo piston, 36 Hensenyuri part, 38, Nosulhoti (fuel passage), 39 - First nozzle, 40 - Second nozzle, 43- auxiliary fuel passage, 55- chef 1~needle. Figure 4 Figure 6 2nd and 1st season! (X) Figure 10 Figure 11 Figure 12 I L total -''tc't. (b) 't(%.

Claims (1)

[Claims] A fixed part provided on the upstream side of the throttle valve in the intake passage, a nozzle body movably disposed on the fixed part, a nozzle provided on the nozzle body for supplying fuel to the intake passage, and supplying fuel to the nozzle. A succinct piston forms a venturi part between the fuel passage and the fixed part, and changes the venturi area by moving toward and away from the fixed part depending on the negative and positive sides of the venturi part. A variable venturi carburetor is equipped with a jet needle that is inserted and changes the nozzle opening area according to the movement of the suction piston, and a second nozzle is arranged in the nozzle body in series with the nozzle, and a second nozzle is disposed between each nozzle and the second nozzle. A variable venturi carburetor, characterized in that it communicates with a fixed part through an auxiliary fuel passage, and the passage area of the auxiliary fuel passage is controlled based on the operating state of the engine.